The alga, Tetraselmis chuii, will be grown on a large scale in the presence of sodium arsenate in enriched "Instant Ocean" medium. This alga grows well at arsenate concentration of 50 ppm expressed as arsenic. The arsenic-containing cells will be homogenized and subjected to classical biochemical separation procedures. Protein, lipid, carbohydrate and nucleic acid fractions will be isolated. The fractions will be purified by high pressure liquid chromatography in order to isolate the arsenic compound(s) formed by the algae. The arsenic compound(s) will be characterized by mass spectroscopy, Raman, infrared and photoelectron spectroscopy and gas chromatography. The knowledge gained from this project may make it possible to begin to learn about the true toxicity of arsenic and its compounds and whether arsenic may, in fact, be an essential trace element.